1. Technical Field
This invention relates generally to powered watercraft, and more particularly to a super high speed watercraft having multiple M-shaped hulls and bow structure that enable performance at over fifty knots.
2. Description of Related Art
The term “M-shaped hull” as used herein refers to a boat hull falling within the scope of one or more claims of U.S. Pat. Nos. 6,250,245; 6,314,903; and 6,526,903. “M-hull craft” and “M craft” are watercraft that include one or more M-shaped hulls. The M-shaped hulls are designed to recapture the bow wave in order to use bow wave energy to create an air cushion for reduced friction drag. An M-shaped hull does this by including a central displacement section with a deck that extends laterally to support two vertical parallel skirts.
The skirts form planing tunnels on opposite sides of the central displacement section such that the skirts recapture the bow wave into the planing tunnels. The recaptured bow wave spirals through the planing tunnels, trapping incoming air and forcing it aft. The planing tunnel ceilings are sloped downward to the approximate water line about mid-ship so that they help compress the aerated water to form an air cushion for lift and reduced friction drag.
U.S. Pat. No. 6,868,798 describes a watercraft with an M-shaped boat hull that enhances the high-speed potential of M-hull craft by using one or more vertical steps in the planing surface of the displacement sections to further reduce friction drag. In addition, U.S. patent application Ser. No. 10/957,914 describes a watercraft having a self proportioning dual-exhaust system that is used to direct gas turbine or jet engine exhaust into the craft's planing surface at the vertical steps, thereby eliminating the vacuum drag and provide added vessel lift. These and other variations of the M-shaped hull have proven effective at the full range of speed, up to approximately fifty knots or so.
In test trials, a craft with a single M-shaped hull demonstrated a speed upwind 15% greater than downwind when operating at thirty to forty knots. That result indicates a dynamic wind lift with an M-shaped hull that increases with higher vessel speed, and it prompts one to think of super high speed watercraft, especially for anticipated future military applications. For super high speeds in the range of fifty to one hundred knots, however, the volume and velocity of wind entering the M-hull craft tends to destroy the bow wave spiral, with the incoming wind replacing the bow wave spiral as the means of forcing air aft under increasing pressure. Thus, the high-speed characteristic of the M-shaped hull is of significant interest, but a need exists for further refinements of existing M-shaped craft in order to enable performance at super high speeds.